import tornado.ioloop
import tornado.web

class MainHandler(tornado.web.RequestHandler):
    def get(self):
        self.write('Hello World!')

def make_app():
    return tornado.web.Application([(r"/",MainHandler),])

if __name__=='__main__':
    app=make_app()
    app.listen(8888)
    tornado.ioloop.IOLoop.current().start()